After one term highlighted by the success of the 1991 Gulf War in Kuwait he lost to Democrat Bill Clinton amid voters' concerns about the economy.

The father of fellow ex-president and namesake George W Bush and 2016 presidential contender Jeb Bush spent two months in hospital in 2012 and 2013, including a stretch in intensive care, for a bronchitis-related cough and associated fever.

Bush also suffers from Parkinson's disease, which has confined him to a motorised wheelchair in recent years.